During World War II, when German U-boats were torpedoing oil tankers off the U.S. East Coast, the War Production Board issued "Certificate of Necessity for Priority Action No. 1" in 1942. It established that the movement of oil by rail would be the highest priority in domestic transportation.

Railroads pressed every available tank car into service, and retrofitted gondolas and box cars to carry oil. By mid-1943, U.S. railroads were moving nearly 1 million barrels of oil each day from the oil fields of Texas and Oklahoma to the Atlantic Seaboard. The previous pre-war high had been 60,000 barrels a day.

But pipelines and trucks replaced trains after the war, and oil transport by rail became less and less important.

Today, with the increase in production in the Bakken oil region of North Dakota, pipeline capacities are maxed out and trains have become the primary alternative to pipelines for shipping crude out of the Bakken.

According to the Association of American Railroads (AAR), about 200,000 tank-car loads of crude oil rode the U.S. rails in 2012, compared to about 9,500 in 2008.

The North American oil boom has meant big bucks for U.S.
railroads, especially to ship the lighter Bakken crude to the East Coast refineries that can't handle the heavier, dirtier tar sands oil from Canada.

It's a lot easier, and arguably safer, to move crude oil by rail than by pipeline. But it is only safer if the railroads carrying the oil are safe.

The Montreal, Maine & Atlantic Railway - on whose tracks an unattended oil train got loose and careened into the quiet, lovely, historic village of Lac-Mégantic, Quebec, setting off a massive explosion that left at least 50 people dead - has had accident and incident rates that significantly exceeded the national average for railroads of its size for nine of the last 10 years.

That might have to do with the railroad operating trains with just one engineer. Deregulation and the drive for ever-higher profits ended the days when a freight train had an engineer and a fireman in the cab, and a brakeman and conductor in the caboose.

Those extra men provided an extra margin of safety. But the caboose has disappeared, and most railroads run their trains with two men. And using remote controls and running one-man trains would save the Montreal, Maine & Atlantic, which owns 510 miles of track in Maine, Vermont and Quebec, about $4.5 million in labor costs.

However, with a devastated village center, dozens of people dead, and contaminated waterways, those savings got eaten up, and then some, in Lac-Megantic.

The AAR claims that 99.9977 percent of all hazardous materials shipped by rail reached their destinations safely in 2012, and that the amount of oil spilled by railroads (2,269 barrels) in 2012 was far exceeded by pipeline spills (474,441 barrels).

When a train with five locomotives and 72 tank cars loaded with crude oil is parked in a freight yard unattended, one can't help but ask why this happened.

When a train this size carrying dangerous cargo is in the hands of one person, is that a prudent thing?

A railroad is responsible for what's carried on its rails. But both railroads and the government agencies in the U.S. and Canada don't talk about hazardous rail cargo, and the first time that most communities find out is after an accident or spill.

There is also concern about many of the tanker cars themselves, which rail regulators in both countries say are old and prone to rupture in a derailment.

With the oil boom, there's a shortage of tanker cars, and the temptation to push equipment to its limits is great.

Add inadequate oversight to the pressure to drive up profits that is overtaking safety and common sense, and it is clear that there needs to be better monitoring and regulation of the rail industry.

Without it, the chances of another Lac-Mégantic fire happening becomes more and more likely.

AR's Chief of Correspondents, Randolph T. Holhut, holds an M.P.A. from the Kennedy School of Government at Harvard University and has been an award-winning journalist in New England for more than 30 years. He edited "The George Seldes Reader" (Barricade Books). He can be reached at randyholhut@yahoo.com.